From owner-freebsd-hackers@FreeBSD.ORG  Mon Apr 21 14:02:00 2008
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 51398106566B
	for <freebsd-hackers@freebsd.org>; Mon, 21 Apr 2008 14:02:00 +0000 (UTC)
	(envelope-from fbsd06+VG=93acc154@mlists.homeunix.com)
Received: from turtle-out.mxes.net (turtle-out.mxes.net [216.86.168.191])
	by mx1.freebsd.org (Postfix) with ESMTP id 277C08FC0C
	for <freebsd-hackers@freebsd.org>; Mon, 21 Apr 2008 14:01:59 +0000 (UTC)
	(envelope-from fbsd06+VG=93acc154@mlists.homeunix.com)
Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178])
	by turtle-in.mxes.net (Postfix) with ESMTP id 35696163F59
	for <freebsd-hackers@freebsd.org>; Mon, 21 Apr 2008 09:34:15 -0400 (EDT)
Received: from gumby.homeunix.com. (unknown [87.81.140.128])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by smtp.mxes.net (Postfix) with ESMTP id BF03823E3EF
	for <freebsd-hackers@freebsd.org>; Mon, 21 Apr 2008 09:34:13 -0400 (EDT)
Date: Mon, 21 Apr 2008 14:34:10 +0100
From: RW <fbsd06@mlists.homeunix.com>
To: freebsd-hackers@freebsd.org
Message-ID: <20080421143410.240f954b@gumby.homeunix.com.>
In-Reply-To: <h9oOUUzCYuqirP9PV+W0Sq20EkI@3jF15V5zTEK556uXK9apbHXi8FQ>
References: <20080419175655.51a37bb2@gumby.homeunix.com.>
	<djKnblBB0JYTUSj+tadwNWUolSw@EEu6nkWAZTlxOp7ENdKMY8AImHg>
	<20080420183135.78b8c710@gumby.homeunix.com.>
	<h9oOUUzCYuqirP9PV+W0Sq20EkI@3jF15V5zTEK556uXK9apbHXi8FQ>
X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.9; i386-portbld-freebsd7.0)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Subject: Re: Yarrow's Counter
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 21 Apr 2008 14:02:00 -0000

On Mon, 21 Apr 2008 14:48:30 +0400
Eygene Ryabinkin <rea-fbsd@codelabs.ru> wrote:

> Good day.
> 
> Sun, Apr 20, 2008 at 06:31:35PM +0100, RW wrote:
> > > this modification seems not to help anything, 
> > 
> > It possibly doesn't help with an attack against Yarrow itself, but
> > it means that 512 bits of entropy, rather than 256 bits, can be
> > read-out from /dev/random.
> 
> The only source of entropy is the entropy pool.  The key and the
> counter are both derived from this pool, so if you will concatenate
> two 256 bit values you will not gain more entropy. 
> ...
> 
> Am I missing something?

If you encrypt the previous value of the counter, instead of zero, the
counter will then depend on all the previous keys, and not just the
current one.   With the default settings any two keys more than one
reseed apart are completely independent.